Process for the manufacture of tubes of cement material



u. ISMAN July 16, 1935.

PROCESS FOR THE MANUFACTURE OF TUBES OF CEMENT MATERIAL Filed March 24, 1953 Patented July 16, 1935 UNITED STATES PROCESS FOR THE MANUFACTURE OF TUBES OF CEMENT MATERIAL Umberto Isman, Trieste, Italy Application 4 Claims.

This'invention relates to the manufacture of tubes or tubular bodies of hydraulic cem-ent material mixed with fibrous or any other substance.

Broadly speaking, the quality of an article, particularly when of small thickness relatively to its area, will be improved by the compactness of the material of which it is composed and said compactness will increase with the increasing of the specific pressure to which the material is subjected.

Hydraulic or mechanical pressure is generally used for the manufacture of flat or nearly fiat articles.

Various systems have been proposed for the manufacture of tubular bodies, as for instance the winding of a thin sheet issuing from a rolling mill or a machine of the kind used in paper manufacture or the like round a moulding cylinder; in its dry or wet state moulding of the material by stamping or casting in moulds; pressing of the material against an outer jacket by means of an inner expansible core; cehtrifugating of the material in moulds, etc.

All the above systems though giving good results in the practice show some drawbacks, which are eliminated by this invention. The centrifugal method for instance shows the following drawbacks. The material has to undergo a considerable pressure which is created exclusively by its centrifugal force: therefore its peripherical speed must be very high and the number of turns to be imparted to the mould must reach sometimes several thousands per minute, the machinery is therefore very complicated and expensive.

Moreover in the case of a composite material, such as asbestos-cement, these two substances having different specific weight and volume, will be separated by the centrifugal force, so that the heavier material will be brought towards the out: side and the lighter material toward the inside of the tube; the purpose for which a composite material has been used is therefore not attained.

This invention is based on thefollowing principle: The material or mixture of materials used for the manufacture of the tube are moulded in any suitable manner, for instance in the way here after described, and the pressing of the material required for obtaining a perfectly waterproof tube also able to withstand high pressures is effected by a pressing roller rotating loosely within the mnuld. which rotates on its horizontal axis.

The fundamental principle of this invention consists in that the static pressure normally used is replaced by a dynamic rolling pressure.

The advantages obtained by said method are March 24, 1933, Serial No. 662,603 In Italy March 24, 1932 clearly seen: itwill be possible to manufacture tubes provided with sleeve joint in a single piece, tubular bodies with undulated or otherwise shaped generatrix, and to obtain extreme simplicityof machinery, a compact waterproof and strong material, possibility of manufacturing reinforced tubes of great resistance, tubes provided with inner or outer coating of a material other than that of the tube body, for instance an acid proof coatmg.

The annexed drawing shows, by way of example, an apparatus for carrying out the process according to this invention.

Fig. 1 shows the mould during the filling step in axial section.

Fig. 2 is an axial section of the tube pressing apparatus.

Fig. 3 is a cross section thereof and shows the tube at the starting of the pressing operation.

Fig. 4 is a section similar to Fig. 3 showing the finished tube.

Assuming it is desired to manufacture tubes of Y asbestos-cement, the asbestos fibers of about 5 m/m'. to m/m. length are fully opened in elementary fibres and mixed in the dry state in any proportion, for instance 15%, with the cement, so that each fiber is coated by a cement film. To said mixture obtained by means of a mixer of any type, constituted for instance by a horizontal tube provided with inner ribs and rotating on its axis, water is'added in a quantity which is strictly necessary for the setting of the cement. The percentage of water may be of about 25% according to the moisture contents of the asbestos and if; sprayed. on the mixture in a chamber provided with water atomizers, the supply being controlled according to the quantity of material which is passed in said chamber.

The material thus prepared is introduced, as shown in Fig. 1, into the vertical mould I by means of a filling device. Said filling device is composed of a mandrel 3 provided with a conveyor worm 4 taking a predetermined constant quantity of material off a container. The material canalso be fed by a measuring automatic conveyor. The lower end of the mandrel carrying the worm is provided with a thread 5 having the purpose of pressing the material forming a spiral band the pitch of which depends on the quantityof material and speed of rotation of the mandrel.

The mandrel carrying the conveyor worm and pressing threaded end is kept centrally to said worm, the outer diameter of which is equal to the 'inner diameter of the mould. The mandrel introduced into the empty mould is gradually raised as the mould is being filled with material. A projection N5 of the mandrel under the pressing worm will maintain the shape of the half-pressed material so that when the filling is finished and the mandrel is out of the mould, said mould will contain a tube 1 in the half pressed state and having a greater thickness than that of the finished tube.

The material from the loose state, as above described, in the position 6 is brought to the halfpressed state, Fig. '7. It will then be pressed to the final thickness in such a way as to obtain a perfectly compact material. A centrifugal rolling is therefore effected.

A metallic cylinder 9 having an enlargement It] at one of its ends is introduced in the mould. thus filled for the formation of the sleeve. Said cylinder acting as a compressing roller will have a constant weight for length unit; therefore it must be thinner at the englargement zone Ill. The roller may be made heavier by constructing it in the form of lead filled tube in order to in crease the rolling action.

The mould containing the roller is arranged horizontally in the mould carrier I4 fitted in the heads ll. of the rotating apparatus and locked by means of suitable devices l5. At. the beginning of the rolling operation the counter-cones 12 of the heads in which the frustrated ends II of the roller are fitted, are in the, end position so that the roller is centered.

The apparatus is then rotated at a speed which can be of some hundred turns per minute, said speed depending on the diameter, kind of. mate-' rial etc. While the apparatus works the counter cones I2 are gradually withdrawn, so that the roller will compress the rotating material from which it is carried along performing a rolling motion which together with the weight of the roller and its centrifugal force will press the material to the state 8 of complete compactness.

The roller thus led by the counter-cones which are withdrawn slightly in advance of the pressing of the material, cannot for any reason be brought out of center; moreover owing to the abutting rings l3, the tube will'be of constant thickness.

When the rolling is completed, the mould l is first removed from the mould carrier M, then the roller 9, whereupon the mould is opened thus freeing the finished tube of asbestos-cement enclosed in a sheet casing which will protect it ugtil the setting of the cement has taken place.

The mould is returned to the filling device while another mould is introduced in the apparatus for the rolling and so on in close cycle. A few minutes are sufficient for the manufacture of a tube through the different steps which are effected automatically.

The filling may be effected in any other Way,

,thus for instance by simply filling the material into the mould, in which a roller of a suitable diameter has been centrally arranged, or shaking the material or introducing it by means of a cure rent of air or in any other way.

The material, which can be of any kind may be filled into the mould in the moistened state as described or in the dry state or partially moistened. In these last two cases the material can be moistened before during or after the rolling operation by spraying atomized'water into the mould or by means of the roller which can be in the shape of a container. If required by the quality of material, the apparatus may be heated to a given temperature. I

The tube can also be formed by two or more layers of the same or different materials and-between said layers reinforcements consisting for instance of a spiral or round bar or any other kind may be interposed.

If convenient the compressing roller may be actuated from the outside and move independently of the mould.

What I claim is:

1. A process for the manufacture of hollow bodies comprising, in combination, spreading on the inner face of a vertical mold a layer of cementitious material, preliminarily packing said layer during its formation and finally pressing said cementitious material to the required thickness by arranging the mold with the tube being made in the horizontal position, introducing a heavy cylindrical bodyinto said tube being formed and subjecting said mold to rotation on its own axis thus causing said cylinder to roll on the cementitious layer.

2. Process for the manufacture of tubular bodies consisting in spreading on the inner face of a vertical mold a uniform layer of cementitious material, preliminarily packing said layer during its formation in an axial direction, arranging the mold with the tube being formed in a substantially horizontal position, and finally pressing the layer until it is of the required thickness by rolling a heavy cylinder on said layer.

3. Process for the manufacture of tubular bodies, consisting in spreading on the inner face of a vertical tubular mold a layer of cementitious material, by pouring said material between the mold and a core having helical ribs, preliminarily packing said layer in an axial direction by rotating said core, arranging the mold with the tube being formed in a substantially horizontal position, introducing a floating pressure roller into said tube, and rotating the mold to cause said roller to roll in said tube, to give the final pressure until the tube is of the required thickness.

4. Process for the manufacture of tubular bodies, consisting in introducing cementitious material into a vertical mold having a rotating core which is axially movable and provided with helical ribs, in rotating said core to uniformly distribute the material on the inner face of the mold and at the same time impart an axial pressure on the layer being formed by virtue of the Weight of said core, and finally pressing said tube until it is of the desired thickness, arr-anging the mold with the tube in a substantially horizontal position, introducing a heavy cylindrical body into said tube while being formed, and

rotating said mold on its own axis thus causing said cylinder to roll on the cementitious layer.

UMBERTO ISMAN.. 

